Objective: To investigate the incidence and influencing factors of term small for gestational age infants (SGA ) in China.
Methods: This study is a multicenter study. Data were collected from Chinese Neonatal Network with term infants, born from May 1st 2010 to February 28th 2014, from 83 nationwide hospitals.
Results: A total of 170 565 neonates were recorded from 83 nationwide hospitals; 144 659 cases were term newborn, and 3 543 neonates were found to be term SGA. The incidence of term SGA was 2.45%. In term SGA, the girl's incidence (2.88%, 1 985/69 003) was higher than boy (2.05%, 1 531/74 707), P<0.001. Furthermore, the incidence of in vitro fertilization (IVF) and artificial fertilization of term SGA was 9.12% (66/724), which was higher than the natural conception (2.42%, 3 465/143 283), P<0.001. The incidence of term SGA in multiple births (30.37%, 741/2 440) was higher than that of single birth (1.97%, 2 787/141 366), P<0.001. The incidence of SGA with maternal age <18 years old was 4.86% (27/556) and was 3.20% (307/9 592) with maternal age > 35 years old, meanwhile both were higher than that with maternal age as 18-35 years old (2.39%, 3 197/133 662). The incidence of SGA with maternal occupation as farmers was 4.67% (854/18 284), which was significantly higher than other professions. The incidence of SGA with maternal education as illiterate and elementary education was 8.65% (187/2 162), 5.17% (397/7 678), respectively, both were significantly higher than those with mother graduated from university (1.72%, 853/49 692). Moreover, the geographical distribution of the main residence of the term SGA mothers showed Northeast Area (1.54%, 30/1 946)and East Area (2.21%, 1 267/57 334) had lower incidence of term SGA than those of Central South Area (2.71%, 493/18 223) and Southwest Area (3.67%, 876/23 852).
Conclusions: The incidence of term SGA was 2.45% in this study, which was influenced significantly by gender, IVF, multiple births, maternal factors (age, maternal occupation, level of education) and geographical distribution. This multicenter study with large data, to a certain extent, reflected status of the incidence and influencing factors of term SGA in China, which will help prevent and treat term SGA.